Writing instrument or tools such as pens have been widely used in daily life, so people not only use it to write, but also as a tool for other purposes. Particularly due to the popularity of intelligent devices such as smart phones, tablets or computers with touch sensitive displays, people often need touch tools, such as a stylus. Such touch tools are neither convenient to carry nor easy to store, so how to use a pen or other writing instrument to carry this type of tool is a purpose of an exemplary embodiment of this invention.